Clamp off your heater hoses for a few minutes,and ck to see that the discharge temp has gotten colder ... If so you have a blend door problem,and should take your vehicle to a repair shop to have it fixed...

my 1999 crown vic is the same way.. one day cold air,the next hot. went to a local parts store, they sold me a fuse "didnt work" freon "didnt work" and lastly a fan cluch switch.. "didnt work".. its so hot it fells like the heater is on...

Make sure your fan clutch is good. I was able to hold mine with a dowel stick and start the truck and it didn't move. After I replaced the fan clutch it blew real cold air it started pulling air past the Ac coils in front of the radiator. Hope this may help U.

Is your A/C compressor turning on? Is it saying on or does it cycle on and off? Do all the vent and heater controls work normally? Look at this info and fill out the diagnostic check sheet, it should help to isolate the problem. http://repairpal.com/blog/Heating-And-Cooling-Issues